求翻译：将从活性污泥中分离筛选出的九种细菌分别投入实验水样，分别停留5天、8天、12天，与原水水样相比，水体COD、BOD5、总氮、总磷指标都有下降，但不同菌株的净化效果不同。是什么意思？

Isolated from the activated sludge the screened nine bacterial invest experimental water samples, respectively, for 5 days, 8 days, 12 days, compared with the raw water, water cod bod5, total nitrogen, total phosphorus indicators have decline, but the purifying effect of different strains.

In the activated sludge separation from filtering out of the 9 types of germs, like water in experiments, respectively, 5 days, 8 days, 12 days, and the water, as water, BOD COD 5, total nitrogen, total phosphorus, and indicators are a decline in the different strains of different purification effec

将从活性污泥中分离筛选出的九种细菌分别投入实验水样，分别停留5天、8天、12天，与原水水样相比，水体COD、BOD5、总氮、总磷指标都有下降，但不同菌株的净化效果不同。

From screening out of nine species of bacteria in activated sludge into experimental samples, respectively, for 5 days, 8 days, 12 days, respectively, compared with samples of raw water, water COD, BOD5, total nitrogen and total phosphorus index has declined, but different strains of purification ef

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